592 SOILS: PROPERTIES AND MANAGEMENT 



grouped under two heads, aerobic and anaerobic. The 

 former work in the presence of oxygen, the latter when 

 air is either lacking or only very slightly present. This 

 grouping is not a distinct one by any means, as many 

 organisms may function not only in air but also when 

 oxygen is lacking. The products, however, are as dif- 

 ferent under these two conditions as if they arose from 

 distinct organisms. 



495. Aerobic action. — When manure is first produced 

 it is likely to be rather loose, and if allowed to dry at 

 once it becomes well aerated. The first bacterial action 

 is therefore likely to be rather largely aerobic in nature. 

 Transformations are very rapid and are accompanied by 

 considerable heat, ranging from 100° to 150° F. and some- 

 times higher. This action falls largely on the simple 

 nitrogenous compounds. Urea is principally affected, 

 and will very quickly disappear from well-aerated manure. 

 The reaction is as follows : — 



CON 2 H 4 + 2 H 2 = (NH 4 ) 2 C0 8 



The ammonium carbonate is a volatile compound, and 

 on the least exposure and evaporation of the manurial 

 liquids it changes into ammonia and carbon dioxide. 

 Thus nitrogen may be rapidly lost from manure by the 

 unwise allowing of excessive aerobic decay and decom- 

 position to proceed. 



This complex group of aerobic putrefactive organisms 

 also attack to a certain extent the more complicated ni- 

 trogenous compounds, as well as some of the simpler car- 

 bohydrates contained in the solid and the liquid portions 

 of the manure. More carbon dioxide therefore results, 

 as well as certain simplified products which ultimately 

 may be reduced to such a form as to be available as plant- 



